A light emitting diode is a p-n junction diode having a characteristic in which electric energy is converted into light energy, may be formed by compounding Group III and Group V elements or Group II and Group VI elements on the periodic table and may realize various colors by adjusting a composition ratio of the compound semiconductor.
Nitride semiconductors are attracting a great attention in the development fields of optical devices and high power electronic devices due to high thermal stability and wide band-gap energy thereof. In particular, an ultraviolet (UV) light emitting diode, a blue light emitting diode, a green light emitting diode, a red light emitting diode and the like using the nitride semiconductor are commercialized and used widely.
The UV light emitting diode (UV LED) is a light emitting diode which emits light in a wavelength range of 200 nm to 400 nm. The ultraviolet light emitting diode may be configured with a short wavelength and a long wavelength depending on an application. The short wavelength may be used for sterilization or purification, and the long wavelength may be used for an exposure machine, a curing machine, or the like.
Meanwhile, the ultraviolet light emitting diode has a problem that light acquisition efficiency and light output are lower than those of the blue light emitting diode, which serves as a barrier in practical use of the ultraviolet light emitting diode.
For example, a Group III nitride used in an ultraviolet light emitting diode may be widely used in a range from visible light to ultraviolet light, but efficiency of ultraviolet light is lower than that of visible light, which is due to the fact that the Group III nitride absorbs ultraviolet light as the Group III nitride goes toward a wavelength of ultraviolet light and internal quantum efficiency is lowered due to low crystallinity.
Since an indium (In) composition of the ultraviolet light emitting diode is low, it is difficult to see an In localization effect compared to the blue LED in a quantum well. Therefore, in the related art, a control and crystallinity of threading dislocation coming from a lower layer affect brightness of a chip.
Meanwhile, in order to improve light extraction efficiency, the ultraviolet light emitting diode forms a light extraction pattern on an n-type semiconductor layer by a method such as photoelectrochemical (PEC).
However, the n-type semiconductor layer may cause over-etching of the light extraction pattern, and the over-etching causes a short. That is, a yield of the light extraction pattern of a general n-type semiconductor layer by the PEC is lowered due to a short or the like.